Air preheater



Dec. l, 1931. vw. E. Down, JR 1,834,579

AIR PREHEATER- Filed Aug. 4, 192e z'sheets-sheet 1 lNvENToR Wwf. ys f. Zon/af). n; BY

1S W ATTORNEY A Dec. l, 1931. w. E. Down, JR

AIR PREHEATER 2 Sheets-Sheet 2 Filed Aug. 4, 1926 INVENTOR BY (g1/1M (fp/LW ATTORNEY Patented Dec. 1, 1931 i UNITED #STATES PATENT OFFICE WYLLYS DOWD, JR., 0F NEW YORIfN. Y., ASSIGNOR T0 FOSTER WHEELER CORPO- RATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK AIR `PREHEATER AApplication. Afiled August 4, 1926. Serial No. 127,167. y

More specifically, the obj ect of the invention l is the construction of an air'preheater in a novel manner, characterized by the` effective manner in'which the availableheat in the furnace gases coming 'tothe preheater is utilized, and by the mechanical simplicity'and compactness of the preheating provisions,

and by the efficiency and low cost per square foot of heating surface attained.

The various features of 'novelty which characterize my invention areV pointed out with particularity in the claims annexed to and forming a part of this specification. For

a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described tion. A

Of the drawings: f

Fig. 1 is an Velevation insection on the line 1 1 of Fig. 2;

Fig. 2is'a rear view of the preheater-and as shown in Fig. 1, by a partition E4 boiler arrangement partly broken away; v

Fig. 3 is a side elevation with the housing brokenv away showing a modified preheater arrangement for another type of boiler furnace; and i Fig. t Vis a rear view' with parts broken away for the preheater of 3.

In the drawings, Figsll and 2, 1 have illustrated the use of my inventionA in connection with a blast furnace gas'fired boiler A, but it will be understood that therinvention is adapted for'use in connection with any boiler y B is the air preheater C. The waste heating "gases pass directly down between the horizontally extending tubes ofthe air preheater preferred embodiments 'of `my inven- ,Y y

` each tube sheet and thecorresponding end this outlet, as shown, opening through the rear wall of the boiler housing adjacent the top of the latter. By means of an induced draft fan and stack (not shown) the heating gases are drawn down over the horizontal water tubes B. of the feed water kheater B, which has a water inlet B2 and water outlet Situated. directly below the economizer and then pass tothe stack and atmosphere.

The air preheater C, constructed in accordance with the present invention, issituated in `the lower part of the housing in which the economizer B is' located. As seen in Figs. 1 and 2, the preheater is made up of four distinctbanks oftubes @through which air is passed and over which furnace gases pass, all of which tubes extend horizontally and transversely to the boiler housing. At the endsv of the intertube space ofthe preheater arevertical tube sheets D and D2, in which the opposite ends" of the `tubes are secured. Between wall of the preheater is a chamber space.

kEach space is divided centrally by a` solid,

vertical partition E3. One of the portions of' each chamber so divided is subdivided tions E3 and E4 the chamber space at the left end of the preheater is divided into three subchambers E, E and E2 as shown in Fig. 1, vthe sub-chamber E comprising half of the V*chamber while the sub-chambers E and E2 comprise the vother half of the chamber. The 'chamber at theother end of the preheater chamber is divided by the partitions E3 and E5 into three sub-chambers e, e and e2; the sub-chamber e being directly opposite to the sub-chambers E and E2, and the sub-chambers e and e2 directlyiopposite Ato the subchamber'E at the opposite end of the preheater. i i

The preheater is thus designed `to pass air through the preheater tubes in two ,distinct- U-shaped streams, the legs of which are parallel but extend in opposite directions leaving the preheater at opposite ends by the conduits H and H and going to opposite sides of the combustion chamber A. To this end, in the construction shown in Figs. l and 2, the air going to the right side of the combustion chamber as seen from the front,-'enters the lower sub-chamber E2, and by means of the partitions E3 and E4, is directed to the tubes C., .through which` it lflows to the opposite end of the preheater to sub-chamber c rising vertically and returning through the tubes to t-he sub-chamber E in the upper right side of the preheater as seen in Fig. l. From this chamber' the heated air is piped by the conduit H tothe combustion chamber.. The air to the far side of the combustion chamber enters the sub-chamber e2 at .the right side of the l preheater .as shown in Fig. 2, ,passes through the .tubes C to the sub-chamber E, rising and returning by way of the tubes to the sub-chamber e', and is piped toair inlets P in the far Wall of the combustion chamber by the conduit H. Air fans (not shown) are used to force the air to the preheater. Vertically and horizontally spaced along the rear wallof the `preheater are small soot Yblower-'nozzles F arrangeclto be connected to an air or steam supply for periodically cleaning the accumulated soot Yand dust from the s preh'eatertllbes. y y

It will Abe observed-that theV preheater arrangement lends itself to effective counter- -current operation. The incomingfairzabsorbs Aheat from they heating gases passing around the banks oftubes, ,and still lfurther absorbs heat whiler .travelling through the upper 'banks of tubes. Y .H

In Figs. 3 and l, .a modified arrangement of the preheater is .shown .adapted for use with Stoker fired boilers. The air is forced through the preheater ytubes in two separate streams bythe fans K and K2. The flow of `air is seen to be the reverse of that shown in Figs. l .and 2 as the streams enter bythe upper banks of tubes M and M2 and leave the preheater by the lower banks oftubes'M3 yand M, The counter-current effect is obtained by .passing the heating gasesk from `the coinbustion chamber by way of the lpassages N and N2 up through the preheater tube chamber. The induced .draft fan K3 is used to assist the waste gas circulation. The partitions, tube sheets and end chambers are constructed as was shown in Figs. l and 2.

The preheater construction .shownin the present application is especially adapted for boiler constructions wherein it is desirable to have equal supplies of hot air to inlets at both sides of the combustion chamber. It is obvious that the connections from the preheater outlets to the combustion chamber are shortened by the arrangement. There are special advantagesin the present preheaterconstruction over air preheater constructions .may-be made in the form -of the apparatus disclosed without departingV from the spirit now in general use in which the air passing to opposite sides of the furnace is preheated in separate end to end banks of tubes. The tubes in such prior constructions are only about half as long as it is practically feasible y.and .desirable to make the ytubes vin ythe use scribed the best form `of-embodiment of my invention now ,known to me, it will be apparent to thoseskilled inthe art that changes of my invention asset forth in the appended claims and that in some Cases Ycertain features of rmyinvention may be used to advantagewithout a corresponding use of other one and partly through the other of said Itwo 105 similar paths of iiow with the direction of air llow .along one of said paths opposite to the direction of air How alongthe other path. 2. In an air preheater, means for passing heating gases `through said heater in a vertical direction, means for passing .a current of air in a U-shaped path transversely .to said flow of heating gases7 and means for passing a second and separate current of air through said heater in a U-shaped path transu versely to said flow of heating gases and in an opposite ydirection to said first mentioned current `of air.

3. In an air preheater, a housing, a vplurality of banks of air conduits alongside of each 120 other in said housing and arranged to provide `two separate paths vof air How in opposite directions, and means for passing heating gases vertically thro-ugh said housing in a path normally to saidpaths of airflow and in 125 contact with said conduits.

4. In an air preheater, the combination with ya housing, ofl parallel tubes extending across said housing, means for passing .heats ing gases vertically thro-ugh the intertube 130 space within the housing, and connections to the ends of the tubes providing two U- shaped paths of flow for the air to be preheated, each leg of each U-shaped path of air flow comprising a plurality of said tubes, the ends of one of said U-shaped paths of How being at one end, and the ends of the other U-shaped path of flow being at the other end of the preheater.

5. An air preheater having a rectangular housing, vertical tube sheets adjacent to opposite ends of said housing and spaced therefrom to form end chambers therebetween, a plurality of parallel tubes extending horizontally in said housing and having their ends opening into said end chambers, a central vertical partition in each of said yend chambers dividing the corresponding Chamber into sections, a horizontal partition in two diagonally opposite sections of said end chambers separating the upper and lower portions of the corresponding sections and forming two separate side by side Ushaped paths of flow through said tubes and end chambers terminating at opposite ends of said preheater.

Signed at New York city, in the county of New York, and State of New York, this 29th day of July, A. D. 1926.

WYLLYS E. DOWD, JR. 

